I have changed password in my Ubuntu server. But I've noticed I still cann ssh becaus I have done ssh-copy-id before. I want to revoke access to myself and other users who may have copied the ssh key.
I have already changed the password, now I need something like creating a new key or revoking access to users who had been granted.
~user/.ssh/authorized_keys to disallow user from connecting using any ssh keypair; or edit it to delete specific keypairs.
If they all have been granted access to same user on server, then you should open
/home/user/.ssh/authorized_keys - this is usually the path to file where ssh stores public keys of users that are allowed to login.
If is is there, then just delete keys that you want - they usually have comment after them indicating username/hostname where they were generated.